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Logical Statements And Conclusions To Essays

The conclusion of an argumentative piece of writing (or speech) is the claim that the author intends for you to accept on the basis of the reasoning that has been given.It is the central point, or the proposition that all of the other claims support.Recall that a successful argument is supposed to be a set of claims, reasons, or premises that are true, and when they are taken jointly, they logically imply the truth of the conclusion.So accepting the premises will also require us to accept the conclusion as true.

There many be several points being made, or there may appear to be several arguments for different conclusions.If the piece is composed well, those subordinate arguments will lend support to the final, central thesis.It may help to ask, “which of the claims being argued for is the broadest in scope or the most general?”That will often reveal the central thesis.

How does one find the conclusion in a piece of argumentative writing?Three suggestions:

1.  Innate sense—In general, our innate sense of the main point is a pretty reliable guide to the conclusion.Read all of the claims carefully and ask yourself, “what is the central claim being made here?What is the main point that the author wants me to accept?

2.  Conclusion Indicators—There are a number of explicit terms that we use to indicate that a conclusion follows from some reasoning.They can be obvious: 

therefore

in conclusion

it follows that

we should draw the conclusion that

X implies Y

So, ....

Or they can be less obvious:

because

since 

hence

thus

So look for explicit conclusion indicators.

3.  Logical Structure—We have been studying formalized arguments that have valid or cogent structures.If a passage contains claims that can be represented at “If P then Q,” and “Q,” and “P,” for instance, the obvious conclusion that could follow from what the author has said is “Q” from the premises “If P then Q,” and “P.”If we interpret the conclusion as “P,” in this case, we would be attributing an invalid, and poor argument to the author.If the author makes that sort of egregious logical mistake, and it is clear that she does in the passage, then that is her mistake and you must take her at her word.(Your first criticism of the reconstructed argument should be that it is invalid, so the conclusion does not follow from the premises even if they were true.)But if the athor is being careful, and we are being charitable, attribute a valid argument to them if it is consistent with what is in the passage, all other things being equal.That is, get a sense of what the logical structure of the argument is, and that can help you identify the conclusion, if other methods fail.

4.  Implied conclusions and premises.  In some cases, a premise or the conclusion are clearly implied by what the author says and by the logical structure of the passage.  That is, a premise isn't stated explicitly, but it is clearly needed to make the argument valid or cogent, and the author has taken it for granted that the reader will see the implication.  In these cases, take what has been explicitly written and try to put into either a valid or cogent argument form, and see if there is a missing premise that, if added, would make the argument valid of cogent, and the author appears to have assumed it.  Implicit conclusions work the same way.  See the linked webpages and the lectures for Reconstructing Arguments for more information.  

Examples

A.  I need to get a flu shot.  If you want to decrease your chances of getting the flu, then you need to get the shot.  I can’t afford to get sick this year. 

B.  If we bring our troops out of Afghanistan too quickly, the government there will collapse.  And the U.S. cannot suffer through the embarrassment of the foreign relations failure of a government collapse there.  So we should not bring the troops out too quickly. 

C.  No Republicans are suitable to be president because no Republicans are in support of gay marriage.  And only candidates who are in support of gay marriage are suitable to be president. 

D.  The only abortions that should be legal are ones that are performed to protect the life of the mother.  The value of one human being’s life is more important than any consideration except the life of another person.  And a fetus is a human being. 

E.  If follows that all liberals are pro-choice since all liberals are progressives.  And all progressives are Democrats.  And all Democrats are pro-choice.

Answers:

A.  I need to get a flu shot.  

B.  We should not bring the troops out of Afghanistan too quickly.  

C.  No Republicans are suitable to be president.  

D.  The only abortions that should be legal are ones that are performed to protect the life of the mother.  

E.  All liberals are pro-choice.  

Finding Premises

When we reconstruct arguments, we start by figuring out what the conclusion is.  What is the main point the author is trying to convince us of?  Once we have determined what that target is, then we can work backwards to reconstruct the reasoning that the author intends for us to follow to get there.  The goal with a strong argument for some conclusion that you don't already believe is to take grounds, or evidence, or premises that you do accept and then show how those claims logically imply the conclusion, so if you're reasonable, then you'll accept the conclusion.  

When we search for the premises, we should ask ourselves this question:  what are the reasons that the author is giving us that she thinks imply the conclusion?  An important guide to finding those should be our knowledge of how deductively and inductively arguments structures work.  With deductively valid or inductively cogent inferences in mind, we should ask, "What are the reasons here that fit into good logical inference structures that could imply the conclusion for the author?  In many cases, particularly in the examples for this class, the reasoning will already employ some basic logical inferences and we can recognize premises and their role in that reasoning.  

Consider this example from above:

B.  If we bring our troops out of Afghanistan too quickly, the government there will collapse.  And the U.S. cannot suffer through the embarrassment of the foreign relations failure of a government collapse there.  So we should not bring the troops out too quickly. 

In this case, the last sentence is the conclusion.  That means that the other sentences are either premises or they are extraneous.  And we are familiar with "If P then Q" inferences.  So the first sentence is clearly a premise:  "If we bring our troops out of Afghanistan too quickly, the government there will collapse."

The second sentence is a premise too, but we can eliminate the "And" as extraneous:  "the U.S. cannot suffer through the embarrassment of the foreign relations failure of a government collapse there."

Consider example E:  

E.  If follows that all liberals are pro-choice since all liberals are progressives.  And all progressives are Democrats.  And all Democrats are pro-choice.

"All liberals are pro-choice." is the conclusion, but we leave off the "Since all liberals are progressives," because "since" separates the conclusion from a premise.  

If we list the premises in order, is this argument valid?  

1.  All liberals are progressives.

2.  All progressives are Democrats.  

3.  All Democrats are pro-choice.  

________________________

4.  Therefore, all liberals are pro-choice.  

Yes, this argument is valid.  We need all of the remaining sentences besides the conclusion to make a valid argument.  So the rest are premises.  

Consider this argument:  

Clearly, the governor is lying about how much he paid in state taxes last year.  Most of the things that the governor says when he is speaking to the press are lies. The last time he spoke to the press about firefighter pensions, he misrepresented the amounts.  And when he was speaking to the press, he told them he paid $17,040 in taxes last year.  

In this case, "The governor is lying about how much he paid in state taxes last year." is the conclusion.  

We might be tempted to list everything else as premises: 

1.  Most of the things that the governor says when he is speaking to the press are lies. 

2.  The last time he spoke to the press about firefighter pensions, he misrepresented the amounts.  

3.  When he was speaking to the press, he told them he paid $17,040 in taxes last year.

______________________________________

4.  Therefore, the governor is lying about how much he paid in state taxes last year. 

This is a good start, but line 2 is extraneous.  It's not needed to make the argument cogent, and it doesn't really add anything logically to the argument.  The firefighter point isn't necessary as a premise.  This reconstruction and list of premises is better:

1.  Most of the things that the governor says when he is speaking to the press are lies. 

2.  When he was speaking to the press, he told them he paid $17,040 in taxes last year.

______________________________________

3.  Therefore, the governor is lying about how much he paid in state taxes last year.

So "The last time he spoke to the press about firefighter pensions, he misrepresented the amounts." is NOT a premise in this argument.  It is unnecessary.  The lesson here is that not everything that an author says is an essential logical part of the argument.  And finding premises requires more thought than merely listing all of the other non-conclusion sentences verbatim.  Trim and adjust the premises so that they conform to the logical structure that the author is employing.  

Logic in Argumentative Writing

Summary:

This resource covers using logic within writing—logical vocabulary, logical fallacies, and other types of logos-based reasoning.

Contributors: Ryan Weber, Allen Brizee
Last Edited: 2018-02-09 12:53:15

This handout is designed to help writers develop and use logical arguments in writing. This handout helps writers analyze the arguments of others and generate their own arguments. However, it is important to remember that logic is only one aspect of a successful argument. Non-logical arguments, statements that cannot be logically proven or disproved, are important in argumentative writing—such as appeals to emotions or values. Illogical arguments, on the other hand, are false and must be avoided.

Logic is a formal system of analysis that helps writers invent, demonstrate, and prove arguments. It works by testing propositions against one another to determine their accuracy. People often think they are using logic when they avoid emotion or make arguments based on their common sense, such as "Everyone should look out for their own self-interests" or "People have the right to be free." However, unemotional or common sense statements are not always equivalent to logical statements. To be logical, a proposition must be tested within a logical sequence.

The most famous logical sequence, called the syllogism, was developed by the Greek philosopher Aristotle. His most famous syllogism is:

Premise 1: All men are mortal.
Premise 2: Socrates is a man.
Conclusion: Therefore, Socrates is mortal.

In this sequence, premise 2 is tested against premise 1 to reach the logical conclusion. Within this system, if both premises are considered valid, there is no other logical conclusion than determining that Socrates is a mortal.

This guide provides some vocabulary and strategies for determining logical conclusions.

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